At the frontier between innate and adaptive immunity, dendritic cells (DCs) secrete numerous cytokines and express costimulatory molecules that initiate or enhance natural killer (NK) and T-lymphocyte responses. NK cells also regulate DC physiology by killing immature DCs (iDCs), thus limiting inflammation and inappropriate T-lymphocyte tolerization. In a previous study, we have reported that NK cells from acute myeloid leukemia patients (AML-NK cells) have deficient natural cytotoxicity receptor (NCR) expression. Herein, we analyzed the consequences of such a defect regarding the regulatory role of AML-NK cells in DC physiology. We show that NK cells display poor cytolytic capacities against DCs derived from healthy donor monocytes or derived from autologous leukemic blasts. These data point to a novel defect in the regulation of adaptive immune responses initiated by DCs in AML patients. This may lead to specific T-lymphocyte tolerization by spontaneous or ex vivo expanded iDCs expressing leukemia-derived antigens.